Hidden User$

We have a windows 2000 domain and several remote sites. At one of our sites, I noticed a user account with permissions named domain\username$. Now, when there’s a share called \\server\data$, that indicates a hidden share. Is there such a thing as a hidden user? I’m the admin, and I don’t see any user by that name in AD users and computers, so I can’t delete the name. Normally, after I delete a user, the SID shows up, or it says account unknown, but that’s not the case here. It seems as if it’s correctly resolving the user. The reason I’m concerned is that the user’s name is the name of a former admin that was let go. Without scouring each file, directory, and object, how can I be sure my network is safe?